JP2018005021A - Autofocus module and video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AF function for a business video camera including a lens driving unit and a focal point controller but not having the AF function.SOLUTION: An autofocus (AF) module 50 is inserted into a section between a lens driving unit 40 and a focal point (F) controller 22. The F controller gives the lens driving unit operation instructions to move a focus group 12 to an optical axis direction of a zoom lens on the basis of manual operation. Upon receiving a command to give instructions on AF operation from the F controller, the AF module converts AF-related commands sent from the F controller after this into operation commands with which the lens driving unit can operate and transmits them to the lens driving unit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an autofocus module and a video camera, and more particularly to an autofocus module suitable for use in realizing a video camera having an autofocus function when mounted on a video camera without an autofocus function, and the autofocus module. The present invention relates to a video camera equipped with a focus module.

  A video camera uses a front focus type zoom lens or a rear focus type zoom lens as an imaging lens.

  A video camera equipped with a front focus type zoom lens is designed on the assumption that it will be used mainly by professional photographers such as television cameras. Hereinafter, this type of video camera is sometimes referred to as a professional video camera. Front focus type zoom lenses are less susceptible to changes in brightness (changes in lens F-number) due to zoom operations up to the long focus area, and are advantageous for achieving high magnification. It has features such as less likely to change the zoom ratio based on color, or less likely to cause color shading that changes the color of the periphery of the lens.

  On the other hand, the rear focus type zoom lens has features that the brightness of the lens changes by zoom operation, and the angle of view increases as the distance to the subject becomes shorter, but the entire lens system can be made compact. Because of its features, it is mainly used in consumer video cameras. In a rear focus type zoom lens, because of the property that the position of the focus group is determined by the distance to the subject and the position of the zoom group, it is necessary to move these lens groups in a complex manner during the focusing operation. However, electronic cams have been developed that realize the complicated movement of these lens groups by motor drive controlled by computer instructions. For this reason, it is standard that consumer video cameras equipped with a rear focus type zoom lens have an autofocus function (AF function).

  In a conventional video camera, focus adjustment has been performed by manually moving a focus lens of a photographing optical system of the video camera while viewing a subject image of a viewfinder. However, this manual focus adjustment method has a problem that it is difficult to always perform satisfactory focus adjustment because the focal depth of the long focus lens is deep. Therefore, the following method is disclosed as a method for solving this problem.

  First, combining the manual focusing means and the automatic focusing means, after the focus adjustment of the focus lens by the manual focusing means, an activation signal generated based on the completion of the focusing operation of the manual focusing means or external manual operation is generated. A focus adjustment method is disclosed that performs fine adjustment of focus lens focusing on a high-frequency spatial frequency component that is difficult to visually determine by automatic focusing means that operates in response (see Patent Document 1).

  Also, a focus adjustment method is disclosed in which the focus lens can be moved manually to a required position, and then the focus lens can be smoothly and quickly moved from that position to the position where the focus evaluation value is maximized. (See Patent Document 2).

  Conventionally, in an industrial video camera, when the AF start switch, which is the start switch for executing the AF function, is turned on, the zoom lens is moved to the tele end, and then the focus lens is moved up in the direction of increasing the focus evaluation value. Thus, there has been proposed a method in which focus adjustment is performed by moving the zoom lens to a position where the maximum focus evaluation value is given, and returning the zoom lens to the original position after the focus adjustment is completed. However, if the focus lens position is greatly deviated from the maximum point of the focus evaluation value, it may be difficult to detect the direction of increase of the focus evaluation value even if wobbling is performed. Cost. Therefore, an adjustment method is disclosed in which the direction in which the focus evaluation value increases is detected immediately to shorten the AF operation time and improve the AF operation performance (see Patent Document 3).

Japanese Patent Laid-Open No. 1-158881 (Japanese Patent No. 2504497) JP-A-8-36129 (Patent No. 3412713) Japanese Patent Application Laid-Open No. 11-109215 (Japanese Patent No. 3841241)

  As described above, professional video cameras have an AF function for some products. However, in the professional video camera, the focus group of the zoom lens and the lens driving unit that changes the position of the zoom group, and the focus group of the lens group are moved in the optical axis direction based on manual operation to perform focusing. A configuration including a focus controller (F controller) having a function of outputting a command for instructing an operation to be performed is mainstream, and a camera having an AF function is not common.

  Therefore, if the AF function can be realized simply by adding a module with a simple configuration to the above-mentioned professional video camera that has a lens drive unit and F controller but does not have an AF function, it is extremely industrially difficult. There is a big effect.

  Therefore, an autofocus module (AF module) that can be inserted between the lens drive unit and the F controller for a professional video camera equipped with a lens drive unit and an F controller to realize a video camera with an AF function. The purpose is to provide. It is another object of the present invention to provide a professional video camera including a lens driving unit, an F controller, and an AF module.

  In order to achieve the above object, according to a first aspect of the present invention, an AF module having the following configuration is provided.

  The AF module of the present invention is inserted between the lens driving unit and the F controller. The lens driving unit moves the focus group and the zoom group constituting the zoom lens along the optical axis of the zoom lens. The F controller outputs a command for instructing an operation of moving the focus group and the zoom group based on a manual operation. When the AF module receives a command to start AF operation from the F controller, it changes the autofocus related (AF related) command transmitted from the F controller to a command that can be received by the lens drive unit. Send to the drive.

  This AF module obtains focus information, stores it for a certain period of time during the manual operation, and a central processing unit (CPU: Central Processing Unit) that includes a ring buffer that updates the focus information after a predetermined period of time has elapsed. ).

  The focus information includes a focus evaluation value indicating the sharpness of a photographed image based on a video signal obtained through a photographing optical system including a zoom lens and an image sensor, and a relationship between a focus group position corresponding to the focus evaluation value. Contains information that specifies

  The ring buffer also includes movement direction information that defines the movement direction of the focus group in the focus information, and saves the command to move the focus group in the same direction as the prescribed movement direction when executing the AF operation. Is preferably provided. Further, based on an instruction by a request command from a constantly or temporarily connected evaluation value graph display means, the CPU provided in the AF module outputs focus information stored in the ring buffer, and this evaluation value graph It is preferable to display the relationship between the focus evaluation value included in the focus information and the position of the focus group corresponding to the focus evaluation value in a graph on the display means.

  The CPU included in the AF module of the present invention preferably includes a focus information acquisition unit that acquires focus information from a phase counting pulse output from a rotary encoder having a function as a focus position sensor included in the lens driving unit. .

  The AF module preferably has the following functions.

  The position of the focus group acquired by the ring buffer at the time when the focus evaluation value is calculated using the entire autofocus frame that defines the focus evaluation value acquisition area, which is set in the screen that displays the captured image, and the focus Focus evaluation value that can be regarded as the time when the focus evaluation value was actually generated from the relationship with the position of the focus group that was read at the time when calculation of the focus evaluation value immediately before the time when the evaluation value was calculated was completed Set the generation time.

  The time when the focus evaluation value stored in the ring buffer has been calculated is the immediately subsequent focus evaluation value reception time, and the time when the focus evaluation value immediately before the immediately following focus evaluation value reception time has been calculated is the immediately previous focus evaluation. Value reception time. Then, the position of the focus group at the focus evaluation value generation time is calculated using the relationship between the position of the focus group at the reception time of the immediately following focus evaluation value and the position of the focus group at the reception time of the immediately previous focus evaluation value.

  According to a second aspect of the present invention, there is provided a video camera configured by inserting the AF module according to the first aspect of the invention described above between a lens driving unit and an F controller.

  For a professional video camera equipped with a lens driving unit and an F controller, an AF function can be provided only by inserting the AF module of the present invention between the lens driving unit and the F controller.

  If focus information acquisition means for acquiring focus information based on the phase counting pulse output from the rotary encoder is provided in the AF module, the phase counting pulse can be input to the AF module without using the lens driving unit. As a result, the time delay until the phase counting pulse output from the rotary encoder reaches the AF module can be reduced.

  The focus evaluation value is calculated using the entire surface of the captured image included in the autofocus frame (AF frame) set in the screen for displaying the captured image. For this reason, a finite time that cannot be ignored is required to calculate the focus evaluation value. For this reason, a deviation occurs between the time when the AF module receives the focus evaluation value and the position of the focus group at the time when the focus evaluation value is actually generated. Therefore, there arises a problem that the position of the focus lens from which the optimum focus evaluation value is obtained cannot be accurately grasped.

  This problem can be solved by providing the AF module with the function of calculating the position of the focus group at the focus evaluation value generation time described above.

It is a block block diagram which shows schematic structure of the video camera of embodiment of this invention. It is a follow chart used for description of an interval timer interruption process. It is a flowchart with which it uses for description of the process in which a ring buffer acquires focus information. It is a flowchart with which it uses for description of a focus evaluation value reception process. 10 is a flowchart for explaining a processing process performed after the AF module receives an AF operation start command. It is a figure with which it uses for description of the function of the phase count counter with which CPU of a rotary encoder and AF module is provided.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the block diagram shown in FIG. 1 schematically shows each component so that the present invention can be understood, and the present invention is not limited to the illustrated example. In the following description, specific devices and conditions may be used. However, these devices and conditions are only one preferred example, and therefore the present invention is not limited to these.

<Configuration of video camera>
With reference to FIG. 1, an embodiment of a video camera including the AF module of the present invention will be described. The configuration and operation of the AF module of the present invention will be described in the embodiment of a video camera configured by inserting the AF module. FIG. 1 is a block diagram showing a schematic configuration of a video camera in which an AF module according to an embodiment of the present invention is inserted.

  The video camera of the present invention includes a zoom lens 10 and a video camera housing 20, a lens driving unit 40, and an F controller 22, and further includes an AF module 50 inserted between the lens driving unit 40 and the F controller 22. . The zoom lens 10 includes a lens group of a focus group 12, a zoom group 14, and a master group 16.

  The video camera housing 20 is equipped with a zoom lens 10 that is a photographic optical system, and receives an image picked up by the zoom lens 10 and converts it into a video signal and outputs it (not shown). Is). This video signal is output from the video camera housing 20.

  The F controller 22 instructs the lens driving unit 40 to move the focus group 12 and the zoom group 14 in the optical axis direction of the zoom lens 10 based on a manual operation. Zooming and focusing are performed by moving the focus group 12 and the zoom group 14.

  The lens drive unit 40 includes a CPU 42, a focus motor drive circuit (F motor drive circuit) 44, a focus motor (M) 46, and a rotary encoder 48. The lens driving unit 40 changes the positions of the focus group 12 and the zoom group 14 on the optical axis.

  The F motor drive circuit 44 drives the focus motor 46 based on the drive signal input from the CPU 42, and the focus group 12 and the zoom group 14 of the zoom lens 10 are driven by the focus motor 46 driven by the F motor drive circuit 44. Moving.

  The AF module 50 includes a video branching circuit 52, a high-pass filter (HPF) 54, a gate (GATE) 56, an adder 58, and a CPU 60.

  The rotary encoder 48 outputs a phase counting pulse. The phase counting pulse output from the rotary encoder 48 is input to the CPU 42 and the CPU 60. The CPU 60 has focus information acquisition means (for example, a phase counter) that acquires focus information regarding the position of the focus group 12 on the optical axis from the phase counting pulse. Thereafter, a phase counter is used as focus information acquisition means.

  The positions of the focus group 12 and the zoom group 14 are manually operated by the F controller 22 until the AF module 50 receives a command for instructing the AF operation, but the AF module 50 instructs the AF operation from the F controller 22. When the command is received, the manual operation mode is switched to the AF operation mode, and the AF-related command transmitted from the F controller 22 is changed to a command that can be received by the lens driving unit 40 and transmitted to the lens driving unit 40. To do. In the AF operation mode, the position of the focus group 12 is operated.

  The AF-related command issued from the F controller 22 includes a command for starting an AF operation, a command for specifying a focus evaluation value acquisition area for obtaining a focus evaluation value, which will be described later, or a focus evaluation value acquisition area. There is a command to change However, in a professional video camera that does not have an AF function (conventional professional video camera), these AF-related commands are ignored even if they are transmitted to the lens driving unit 40 as they are.

  Therefore, even when the AF function 50 is added to the conventional professional video camera by inserting the AF module 50 between the lens driving unit 40 and the F controller 22 to provide the AF function, the F controller 22 It is necessary to convert the AF-related command to be an operable focus operation command so that it can be transmitted to the lens driving unit 40. Therefore, when receiving a command for instructing the AF operation to the CPU 60 provided in the AF module 50, the AF related command from the F controller 22 is changed to a command that can be received by the lens driving unit 40, and the lens driving unit 40 is changed. Pre-programmed to transmit.

  The video signal formed by the zoom lens 10 is output from the video camera housing 20 and input to the video branch circuit 52. The video signal is branched by the video branching circuit 52 and output to a viewfinder (not shown) or the like, and a focus evaluation value indicating the sharpness of a captured image generated from the video signal is obtained. It is also input to HPF54.

  The HPF 54 extracts a high frequency component included in the luminance signal of the captured image. Since the extracted high-frequency component contains more as the sharpness of the photographed image is higher, the average sharpness of the photographed image in the integration range can be quantified by integrating the high-frequency component. . The high frequency component that has passed through the HPF 54 is input to the GATE 56. This GATE56 is a circuit that extracts only the signal corresponding to the AF frame that defines the focus evaluation value acquisition area set in the screen that displays the shot image, and only extracts information about the subject that appears in this AF frame. To do.

  The digital signal extracted by the GATE 56 is input to the adder 58 and the digital signals for one field are integrated. This accumulated value is input to the CPU 60 as a focus evaluation value indicating the sharpness of the captured image.

  The CPU 60 includes a ring buffer (not shown) inside. The ring buffer is configured in a RAM (Random Access Memory) of the CPU 60, and focus information is rewritten and read according to an instruction from the CPU 60. This ring buffer stores the focus evaluation value and the position of the focus group 12 as a pair for a predetermined time during the execution of the manual operation.

  The CPU 60 basically operates as follows depending on whether the AF start switch (denoted as AF switch in FIG. 1) of the F controller 22 is not pressed or pressed. If the AF start switch is not pressed, the control command from the F controller 22 is transmitted to the CPU 42 of the lens driving unit 40 as it is, and the CPU 60 has the focus evaluation value and the position of the focus group 12 on the optical axis. Store in ring buffer. This state is a state in which a manual operation is being executed.

  On the other hand, when the AF start switch is pressed, the focus group 12 is moved to a position where the focus evaluation value is maximized, and automatic focusing is performed. This state is the state of AF operation.

  Normally, the AF start switch is in an off state (a manual operation is being performed), and an on signal (AF operation start command) is transmitted when the photographer presses the AF start switch. That is, when the AF start switch is off, the focus group 12 and the zoom group 14 move based on a signal from the F controller 22 instructing manual operation.

<Manual operation and AF operation>
Hereinafter, a case where the cameraman performs a manual operation and a case where the AF operation is performed by pressing the AF start switch of the F controller 22 will be described separately. The case where the manual operation is executed will be described with reference to FIGS. 2 to 4, and the case where the AF operation is executed will be described with reference to FIG. 5. The process shown in FIGS. 2-4 is only performed while the photographer is manually operating.

≪Manual operation≫
While the manual operation is being executed, a ring buffer provided in the CPU 60 stores the focus evaluation value and the position of the focus group 12 in pairs and stores them at a constant time interval. First, the interval timer interruption process will be described with reference to the flowchart shown in FIG. The interval timer interrupt processing process is a process necessary for the ring buffer provided in the CPU 60 to acquire the focus evaluation value and the position of the focus group 12 as a pair.

  As shown in FIG. 2, the CPU 60 analyzes the command from the F controller 22 to detect that the focus group 12 is manually operated. That is, first, step S10 for determining whether or not the AF start switch is pressed is executed. If the AF start switch is not pressed, step S10 continues to be executed every frame (for example, 16.7 milliseconds) of the captured image capturing operation of the video camera housing 20 until the AF start switch is pressed.

  In step S10, it is determined whether or not the AF start switch is pressed, and if it is determined that manual operation is being performed (when the AF start switch is not pressed), the captured image capturing operation of the video camera housing 20 is performed. In step S12, the CPU 60 executes step S12 for requesting the adder 58 to output the focus evaluation value.

  Subsequent to step S12, step S14 for requesting the CPU 60 to output focus information to the CPU 42 is executed. This focus information is sent from the CPU 42 to the CPU 60 through a transmission path indicated as “absolute position information” in FIG. After step S14 is executed, the process returns to step S10 as shown in FIG.

  When the CPU 60 receives a command from the lens driving unit 40, the CPU 60 extracts focus information included in the command. The focus information is generated by the CPU 60 by counting the pulse signals output from the rotary encoder 48 by the movement of the focus group 12, and expressing the current position of the focus group 12 in a format such as 0000h to FFFFh in hexadecimal, for example.

  In order to obtain focus information with a general focus position sensor (PS) without using the rotary encoder 48, the voltage generated in correlation with the position of the focus group 12 is A / D converted, and the focus position sensor 0000h Generate focus information in the form of ~ FFFFh.

  Here, the focus information reception process for causing the ring buffer to acquire the above-described focus information using the rotary encoder 48 will be described with reference to the flowchart shown in FIG.

  As shown in FIG. 3, first, step S20 is executed in which the CPU 60 determines whether or not the focus information from the CPU 42 has been received. When the CPU 60 acquires the above-described focus information, step S22 for storing this information in a ring buffer provided in the CPU 60 is executed. At the time when step S22 is executed, for example, the acquired focus information is stored for a certain period of time in the variable “FOC_POS” in which the position of the focus group 12 is set in the program.

  The focus group 12 is often composed of a combination of a plurality of single lenses.For example, one of the plurality of single lenses is selected, and the position of the focus group 12 is determined by the principal point position of the single lens. Define. There are other methods for defining the position of the focus group 12, but the position of the focus group 12 can be defined on some basis.

  As a characteristic of the ring buffer, old data is automatically updated when focus information is stored a certain number of times. Since the update interval of the focus information is almost constant (in many cases about 1/60 seconds), in the ring buffer, old data is erased in a certain time during manual operation using the F controller 22 by the photographer, and new data Replaced with data.

  As an example, if you configure a ring buffer that stores 300 pairs of data in which the focus evaluation value and the position of the focus group 12 are paired, assuming that the evaluation value update cycle is 1/60 (seconds), 1/60 Since (seconds) × 300 = 5 (seconds), it is possible to store data during manual operation for 5 seconds. In this ring buffer, data is not updated in a time zone when the focus operation (manual operation and AF operation) is not performed, and the data stored so far is maintained. The above 300 pairs of data are stored in the ring buffer in correspondence with the time when the CPU 60 counts the pulse signal output from the rotary encoder 48 and confirms it as the current position of the focus group 12.

  On the other hand, in step S20, the CPU 60 continues to receive focus information from the CPU 42 until the above-described focus information is acquired.

  Next, a focus evaluation value reception process in which the CPU 60 receives the focus evaluation value generated by the adder 58 will be described with reference to the flowchart shown in FIG.

  As shown in FIG. 4, first, step S30 is executed in which the CPU 60 determines whether or not the focus evaluation value generated by the adder 58 has been received from the adder 58. When the CPU 60 receives the command from the adder 58, the focus evaluation value information in the command is extracted and stored in, for example, the variable “FOC_POS”, step S32 is executed. That is, in step S32, at the focus evaluation value reception time, the focus evaluation value and the position “FOC_POS” of the focus group 12 are paired and stored in the ring buffer. Following this step, step S34 is executed to increment the reference address of the ring buffer in preparation for the reception of the focus evaluation value information sent next.

≪AF operation≫
Next, a case where the AF start switch is pressed and the CPU 60 of the AF module 50 receives a command for starting an AF operation (AF operation start command) and shifts to the AF operation will be described.

  When the AF start switch is pressed and the CPU 60 receives a command for starting the AF operation, the operation proceeds to the AF operation. FIG. 5 is a flowchart showing a processing process (AF operation process) after receiving the AF operation start command.

  As shown in FIG. 5, step S <b> 40 is a step in which the CPU 60 determines whether or not an AF operation start command has been received from the F controller 22. When the AF operation start command is received, the maximum focus evaluation value stored in the ring buffer until just before this reception (maximum value among the multiple focus evaluation values stored in the ring buffer) [Pmax] is extracted. Step S42 is executed. Subsequent to step S42, step S44 is executed in which the position of the focus group 12 where [Pmax] is obtained is extracted from the ring buffer and stored in the variable “FOC_CTL”.

  Subsequent to step S44, the CPU 60 transmits focus information of the focus group 12 defined by the variable “FOC_CTL” to the CPU. Then, the CPU 42 generates a control signal for moving the focus group 12 based on the given information.

  Here, in the CPU 60, the variable “FOC_POS” that gives the current position of the focus group 12 is read from the phase counting counter, and the difference (position error) from the variable “FOC_CTL” stored in step S44 ER = FOC_CTL−FOC_POS Is calculated. Then, the error signal is amplified as ER × β so as to provide sufficient strength as the error signal provided to the F motor drive circuit 44, and an instruction is given to the F motor drive circuit 44. The amplification factor β is appropriately set corresponding to the F motor drive circuit 44. The F motor drive circuit 44 executes step S46 of driving the focus motor 46 to move the focus group 12 to a position where [Pmax] is obtained.

  When the AF module 50 receives the AF operation start command, the AF operation is executed as described above.

  A rectangular wave pulse output from the rotary encoder 48 and a phase counting counter that receives the rectangular wave pulse will be described with reference to FIG.

  The rotary encoder 48 outputs two types of rectangular wave pulses, phase A and phase B, whose phases are shifted from each other by 1/4 wavelength, and these rectangular wave pulses are directly input to the phase counting counter. This rectangular wave pulse contains information on the moving direction in such a way that the phase shift direction of the B phase with respect to the A phase corresponds to the moving direction information, and the phase counting counter calculates the count number (counter value) of this rectangular wave pulse. Convert to focus information.

  However, in order for the CPU 60 to recognize the actual position of the focus group 12 on the optical axis, the actual position of the focus group 12 (absolute position information) and the focus information (relative position information) read by the phase counter once. ) Must be calibrated. For example, if the entire range in which the focus group 12 can move along the optical axis of the lens is expressed in hexadecimal notation as 0000h to FFFFh, the intermediate position corresponds to 7FFFh. The absolute position of the focus group 12 is defined so as to correspond one-to-one with 0000h to FFFFh. For calibration of absolute position information and relative position information, for example, the position of one end of the movement range of the focus group 12 is set to 0000h, the other end position is set to FFFFh, and the counter value of the current phase counter is This is an operation to determine which value from 0000h to FFFFh that defines the information corresponds.

  By adopting a configuration in which the two types of rectangular wave pulses output from the rotary encoder 48 are directly input to the CPU 60, the time delay until the focus information reaches the CPU 60 is reduced compared to the case where the CPU 60 inputs the rectangular pulses. It can be shortened. When a square wave pulse is input to the CPU 60 via the CPU 42, a time delay in milliseconds occurs, but if it is directly input to the CPU 60, a time delay in microseconds is sufficient.

  The information output from the rotary encoder 48 does not include absolute position information that defines whether the focus group 12 exists at the focus end or the center. The relative position information is output from the rotary encoder 48, and is directly input to the phase count counter of the CPU 60 of the AF module 50 through the transmission path indicated as "relative position information" shown in FIG.

  This relative position information is converted into an absolute position by the phase counter of the CPU 60. That is, as described above, it is necessary to calibrate the relationship between the position of the focus group 12 and the focus information read by the phase counting counter, but the current counter value counted by the CPU 60 while the focus group 12 is stopped is used. By rewriting according to the absolute position of the focus group 12, conversion to the absolute position can be easily performed. After calibration, focus information that gives an absolute position can be obtained simply by reading the value of the counter.

  The AF module 50 stores the movement direction information that defines the movement direction moved to change the position of the focus group 12 in executing the above-described AF operation, so that the same movement direction as that of the specified movement direction is stored. A command for moving the focus group 12 can be given to the lens driving unit 40.

  To move the focus group 12, for example, if the entire range in which the focus group 12 can move along the optical axis of the lens is expressed as 0000h to FFFFh, etc., it is moved with a command to move to a position corresponding to 7FFFh as an example. It can be moved to an intermediate position in the entire possible range. Here, for example, when the focus group 12 starts moving from 0000h toward 7FFFh and moves starting from FFFFh, the operation directions are opposite. If 7FFFh is the position of the focus group 12, a slight stop position error may occur due to backlash between when moving from the 0000h direction and when moving from the FFFFh direction. For this reason, it is desirable to move and stop from the same direction as when the position of the focus group 12 is detected.

  When the moving direction is opposite, the movement of the focus group 12 is overtaken and then returned. For this reason, for example, the AF operation direction when the position of the focus group 12 is detected is “0” when the AF operation direction is in a certain direction (direction in which the movable range is from 0000h to FFFFh), and “1” when the reverse direction is the reverse direction. The focus evaluation value and the position of the focus group 12 are stored together in the ring buffer. In order to execute the AF operation in this way, a ring buffer that stores 300 pairs of data in which the focus evaluation value and the position of the focus group 12 are paired is set to “focus position” for each pair of 1 to 300, “The position of the uncorrected focus group”, “the position of the corrected focus group”, “focus evaluation value”, and “movement direction” are stored. “The position of the uncorrected focus group” and “the position of the corrected focus group” will be described later.

  When it is desired to check the focus information stored in the ring buffer during manual operation or AF operation, it is desirable to be able to display such information. For this reason, it is preferable to provide evaluation value graph display means 24 for displaying the focus information output from the CPU 60 as shown in FIG. The evaluation value graph display means 24 can be realized using a general-purpose personal computer.

  The CPU 60 provided in the AF module outputs the focus information stored in the ring buffer in response to a request from the evaluation value graph display means 24. The evaluation value graph display means 24 displays the focus information (such as a focus evaluation value given as a function of the position of the focus group 12) in a graph.

≪Correction of focus group position≫
Ideally, the focus evaluation value is a focus evaluation value generated from a video signal obtained at the same time as the focus information acquisition time. Strictly speaking, the phase counting counter reads the position of the focus group 12. Focus information cannot be acquired at the same time. For this reason, in many cases, the time lag between the acquisition time of the focus evaluation value and the focus evaluation value cannot be ignored.

  Specifically, the case where the adder 58 is of a type that sequentially captures and reads from the upper left of the screen on which the captured image is displayed will be described. It takes a certain time until the digital signal is integrated and the focus evaluation value is calculated. For this reason, strictly speaking, focus information cannot be acquired at the same time as the actual position of the focus group 12 read by the phase counter. Therefore, when the time for calculating the focus evaluation value by the adder 58 cannot be ignored, the following method is preferably executed.

  As will be described later, the focus evaluation value generation time is regarded as the digital signal reading start time from the scanning line at the center position above and below the AF frame, the position of the focus group 12 at this focus evaluation value generation time is calculated, and the focus information Replacing the actual position of the focus group 12 at the acquisition time with the position of the focus group 12 at the focus evaluation value generation time eliminates the problem of the time lag between the focus evaluation value acquisition time and the focus evaluation value.

  In addition to the type in which the above-described adder 58 sequentially captures and reads from the upper left of the screen, the adder 58 includes a one-frame screen for capturing a captured image from a video signal output from an image sensor included in the video camera housing 20. Are stored at the same time and then read out. Therefore, it is necessary to notify the CPU 60 or the adder 58 of information on the time at which the focus evaluation value is determined in advance by using a dip switch or the like mounted on the AF module 50. A configuration in which the CPU 60 sends it to the CPU 60 together with the focus evaluation value together with the time delay information about how far (milliseconds ago) it is the focus evaluation value of the video with respect to the time when the focus evaluation value is received. By doing so, it is possible to perform the operation for solving the above-described problem of time lag between the focus evaluation value acquisition time and the focus evaluation value.

  Here, description will be made assuming that the adder 58 is a type that sequentially takes in and reads from the upper left of the screen.

  A screen for displaying a captured image used for obtaining a focus evaluation value is displayed on a viewfinder or a personal computer screen (not shown) in response to a video signal output from the video branching circuit 52. The focus evaluation value is calculated from a captured image within the AF frame by setting an AF frame that defines a focus evaluation value acquisition area on the displayed shooting screen. As an example, an AF frame is displayed on a video monitor or computer screen, and the position and size are set using a joystick or mouse.

  If the image sensor included in the video camera housing 20 is an image sensor that captures and reads captured images sequentially, in order to obtain images within the AF frame, from the upper left to the lower right toward the screen displaying the captured images It takes a certain amount of time to sequentially capture and read out the captured images.

  However, the time at which the scanning line at the center position above and below the AF frame is scanned from the left end to the right end can be regarded as the average time for reading the captured image. Since the time for reading one scanning line of the video signal is negligibly short, there is no problem even if the reading start time on this scanning line is regarded as the focus evaluation value generation time when the focus evaluation value is generated.

  Here, the position of the focus group 12 is read from the focus information acquired at the time when the calculation is completed using the entire AF frame, and the focus group 12 is read at the time when the previous focus evaluation value is calculated. A method of calculating the position of the focus group 12 at the focus evaluation value generation time that can be regarded as the time at which the focus evaluation value is actually generated from the relationship with the position will be specifically described.

  As described above, in the manual operation mode, the time when the CPU 60 receives the focus evaluation value generated by the adder 58 from the adder 58 is almost the same as the time when the calculation is completed using the entire AF frame, This time is set as the focus evaluation value reception time in the ring buffer, and this time and the position of the focus group 12 are stored as focus information. Here, the time at which the focus evaluation value stored in the ring buffer has been calculated is the immediately subsequent focus evaluation value reception time, and the time at which the focus evaluation value immediately before the immediately following focus evaluation value reception time has been calculated is The reception time of the immediately previous focus evaluation value

  Immediately after the focus evaluation value reception time is the time when the scanning line of the AF frame is scanned from the upper left to the lower right and the scanning is completed (the time when the lower right is reached), If the time when the scanning line is scanned from the left end to the right end is regarded as the focus evaluation value generation time, the immediately after focus evaluation value reception time is a time after the focus evaluation value generation time. On the other hand, the previous focus evaluation value reception time is a time before the focus evaluation value generation time since it is the time when the focus evaluation value immediately before the immediately subsequent focus evaluation value reception time has been calculated. That is, the focus evaluation value generation time is a time between the previous focus evaluation value reception time and the immediately subsequent focus evaluation value reception time.

  Therefore, the time at which the CPU 60 received the focus evaluation value stored in the ring buffer as the focus evaluation value at the position of the focus group 12 immediately before and after this time, with the focus evaluation value generation time interposed therebetween, respectively. Value reception time and immediately after focus evaluation value reception time.

Here, the time interval between the focus evaluation value generation time and the immediately subsequent focus evaluation value reception time is T _0, and the time interval between the immediately previous focus evaluation value reception time and the focus evaluation value generation time is T ₁ , and the immediately after focus evaluation The position of the focus group 12 at the value reception time is FP _a, and the position of the focus group 12 at the previous focus evaluation value reception time is FP _b .

The above-mentioned “position of the focus group 12 read from the focus information acquired at the time when the calculation was completed using the entire AF frame” is stored in the ring buffer as the position of the focus group 12 at the immediately following focus evaluation value reception time. Means the position FP _a of the focus group 12, and the above-mentioned “position of the focus group 12 read at the previous time” is the ring buffer as the position of the focus group 12 at the previous focus evaluation value reception time. Means the position FP _b of the focus group 12 stored in Further, the position of the focus group 12 at the time when it can be considered that the focus evaluation value is generated means the position FP of the focus group 12 at the time when the focus evaluation value is generated.

The time interval T ₀ and the time interval T ₁ are extracted mainly from the video signal as a digital signal by the GATE 56, and the time required until the focus evaluation value is calculated by integrating the digital signals for one field by the adder 58, etc. It depends on. That is, as described above, since it takes a finite time to calculate the focus evaluation value, it is necessary to know in advance how much this time is, and from the operating speed of the GATE 56 and the adder 58, the time interval T ₀ and to determine the time interval T _1.

Assuming that the focus group 12 has moved at a constant speed from the position FP _a of the focus group 12 to the position FP _b of the focus group 12, the position of the focus group 12 at the midway focus evaluation value generation time is obtained in time proportion. . Under this assumption, the position FP of the focus group 12 at the time of generating the focus evaluation value is expressed by the following equation (1)
FP = FP _a − [(FP _a −FP _b ) × {T ₀ / (T ₀ + T ₁ )}] (1)
Given in.

Here, the position FP of the focus group 12 is referred to as “corrected focus group position”, and the position FP _a of the focus group 12 and position FP _b of the focus group 12 are referred to as “uncorrected focus group position”. As described above, the ring buffer stores “the position of the uncorrected focus group 12”, “the position of the corrected focus group”, “the focus evaluation value”, and “the moving direction” for each pair of 1 to 300. To be configured.

  When the AF operation can be performed on the assumption that the time for calculating the focus evaluation value by the adder 58 is negligibly small, the variables “FOC_CTL” and “FOC_POS” described with reference to FIGS. “Uncorrected focus group position” can be used.

  However, in many cases, as described above, the time for calculating the focus evaluation value by the adder 58 cannot be ignored. In this case, as the variable “FOC_CTL” stored in step S44, the position FP of the focus group 12 at the focus evaluation value generation time obtained by applying the above equation (1) (“corrected focus group Position ”). In step S46, the focus motor 46 is driven to move the focus group 12 to the position FP of the focus group 12 at the focus evaluation value generation time.

  That is, if the time for calculating the focus evaluation value by the adder 58 cannot be ignored, the CPU 60 determines whether or not the focus evaluation value generated by the adder 58 has been received from the adder 58. Step S42 is executed, and step S42 for extracting the maximum focus evaluation value [Pmax] stored in the ring buffer until immediately before receiving the operation start command is executed. Here, the time at which the CPU 60 received the maximum value of the extracted focus evaluation values is set as the focus evaluation value reception time immediately after.

  Subsequent to step S42, step S44 is executed in which the position of the focus group 12 from which [Pmax] is obtained is extracted from the ring buffer and stored in the variable “FOC_CTL”. As the variable “FOC_CTL” stored in step S44, the focus group position FP at the focus evaluation value generation time that is “corrected focus group position” is used, and the variable “FOC_POS” includes the current focus group 12 current value. A variable giving the position is used.

  Subsequent to step S44, the CPU 60 sends the focus information of the focus group 12 defined by the variable “FOC_CTL” to the CPU 42 of the lens driving unit 40, and the difference (position error) from the variable “FOC_CTL” stored in step S44 ER = FOC_CTL-FOC_POS is calculated. The F motor drive circuit 44 drives the focus motor 46 to move it from the current position of the focus group 12 to the focus group position FP at the focus evaluation value generation time (position stored in the variable “FOC_CTL”). S46 is executed.

<Effect of the invention>
As described above, a professional video camera has a configuration including the lens driving unit 40 and the F controller 22, and a camera having an AF function is not common. However, if a device that changes the AF-related commands from the F controller 22 and sends it to the lens drive unit 40 is modularized and commercialized as an AF module 50, a professional video camera that does not have an AF function On the other hand, a business video camera having an AF function can be easily configured simply by adding a single AF module 50 of the present invention.

10: Zoom lens
12: Focus group
14: Zoom group
16: Master group
20: Video camera housing
22: Focus controller (F controller)
40: Lens drive
42: CPU of lens drive
44: Focus motor drive circuit (F motor drive circuit)
46: Focus motor (M)
48: Rotary encoder
50: Autofocus module (AF module)
52: Video branch circuit
54: High-pass filter (HPF)
56: Gate
58: Adder
60: AF module CPU

Claims (18)

A lens group that moves the focus group, the zoom group, and the zoom group along the optical axis of the zoom lens;
Inserted between a focus controller that outputs a command for instructing an operation of moving the focus group and the zoom group based on a manual operation,
When a command for starting an autofocus operation is received from the focus controller, an autofocus-related command transmitted thereafter from the focus controller is changed to a command that can be received by the lens driver, and the command is sent to the lens driver. An autofocus module characterized by transmitting. Defines a relationship between a focus evaluation value indicating the sharpness of a captured image based on a video signal obtained via an imaging optical system and an imaging element including the zoom lens, and a position of the focus group corresponding to the focus evaluation value It comprises a central processing unit including a ring buffer that acquires focus information including information, stores it for a certain period of time during execution of a manual operation, and updates the focus information after a predetermined period of time has elapsed. The autofocus module according to claim 1. The ring buffer stores the focus information including movement direction information defining a movement direction of the focus group,
3. The autofocus module according to claim 2, wherein a command for moving the focus group in the same direction as the movement direction specified in the movement direction information is given to the lens driving unit when performing the autofocus operation. Further, based on an instruction by a request command from the evaluation value graph display means that is always or temporarily connected, the central processing unit outputs the focus information stored in the ring buffer,
The said evaluation value graph display means graphs and displays the relationship between the said focus evaluation value contained in the said focus information, and the position of the said focus group corresponding to the said focus evaluation value, or characterized by the above-mentioned. The autofocus module according to 3. The central processing unit includes a focus information acquisition unit that acquires the focus information from a phase counting pulse that is output from a rotary encoder that functions as a focus position sensor provided in the lens driving unit. Item 5. The autofocus module according to any one of Items 2 to 4. The rotary encoder outputs two types of rectangular wave pulses of phase A and phase B, the phases of which are shifted from each other by 1/4 wavelength, and the rectangular wave pulse is directly input to the focus information acquisition unit,
The relationship between the actual position of the focus group on the optical axis and the focus information read by the focus information acquisition unit is calibrated,
6. The autofocus according to claim 5, wherein the focus information acquisition unit converts a phase shift direction of a B phase with respect to an A phase of the rectangular wave pulse and a count number of the rectangular wave pulse into the focus information. module. The position of the focus group acquired by the ring buffer at the time when the focus evaluation value is calculated using the entire autofocus frame that defines the focus evaluation value acquisition area, which is set in the screen for displaying the captured image. When,
From the relationship with the position of the focus group read into the ring buffer at the time when the focus evaluation value immediately before the time when the focus evaluation value has been calculated is completed,
Set the focus evaluation value generation time that can be regarded as the time when the focus evaluation value was actually generated,
The time at which the focus evaluation value stored in the ring buffer has been calculated is the immediately subsequent focus evaluation value reception time, and the time at which the immediately preceding focus evaluation value reception time has been calculated is calculated. Let it be the last focus evaluation value reception time,
Using the relationship between the position of the focus group at the reception time immediately after the focus evaluation value and the position of the focus group at the reception time immediately before the focus evaluation value,
The autofocus module according to any one of claims 2 to 6, wherein a position of the focus group at the focus evaluation value generation time is calculated. Between the previous focus evaluation value reception time and the immediately subsequent focus evaluation value reception time,
The focus evaluation value generation time is set by the time when the scanning line at the center position in the vertical direction of the autofocus frame is scanned from the left end to the right end,
The time interval between the focus evaluation value generation time and the immediately subsequent focus evaluation value reception time is T _0, and the time interval between the immediately previous focus evaluation value reception time and the focus evaluation value generation time is T ₁ , The position of the focus group at the focus evaluation value reception time is FP _a , the position of the focus group at the previous focus evaluation value reception time is FP _b ,
The position FP of the focus group at the focus evaluation value generation time is expressed by the following equation (1)
FP = FP _a − [(FP _a −FP _b ) × {T ₀ / (T ₀ + T ₁ )}] (1)
The autofocus module according to claim 7, wherein the autofocus module is given by: Extracting the maximum value of the focus evaluation value stored in the ring buffer until immediately before receiving a command for starting an autofocus operation from the focus controller,
The time at which the maximum value of the extracted focus evaluation value is read as the immediately after focus evaluation value reception time,
Calculate the difference between the current position of the focus group and the position FP of the focus group at the focus evaluation value generation time,
9. The autofocus module according to claim 8, wherein the focus group is moved to a position FP of the focus group at the calculated focus evaluation value generation time. A zoom lens including a lens group of a focus group, a zoom group, and a master group;
A lens driving unit that moves the focus group and the zoom group along an optical axis of the zoom lens; and
A focus controller that outputs a command for instructing an operation of moving the focus group and the zoom group based on a manual operation;
Upon receiving a command inserted between the lens driving unit and the focus controller and starting an autofocus operation from the focus controller, the lens driving unit sends an autofocus-related command transmitted thereafter from the focus controller. A video camera comprising an autofocus module that changes to a receivable command and transmits the command to the lens driving unit. The autofocus module is
Defines a relationship between a focus evaluation value indicating the sharpness of a captured image based on a video signal obtained via an imaging optical system and an imaging element including the zoom lens, and a position of the focus group corresponding to the focus evaluation value It comprises a central processing unit including a ring buffer that acquires focus information including information, stores it for a certain period of time during execution of a manual operation, and updates the focus information after a predetermined period of time has elapsed. The video camera according to claim 10. The ring buffer stores the focus information including movement direction information defining a movement direction of the focus group,
The autofocus module, when executing an autofocus operation, gives a command to the lens driving unit to move the focus group in the same direction as the movement direction defined in the movement direction information. The listed video camera. Further, based on an instruction by a request command from the evaluation value graph display means that is always or temporarily connected, the central processing unit outputs the focus information stored in the ring buffer,
12. The evaluation value graph display means graphs and displays the relationship between the focus evaluation value included in the focus information and the position of the focus group corresponding to the focus evaluation value. 12. The video camera according to 12. The lens driving unit includes a rotary encoder having a function as a focus position sensor,
The rotary encoder outputs a phase counting pulse,
The video camera according to claim 11, wherein the central processing unit includes a focus information acquisition unit that acquires the focus information from a phase counting pulse output from the rotary encoder. . The focus information acquisition means is formed in a central processing unit provided in the autofocus module,
The rotary encoder outputs two types of rectangular wave pulses of phase A and phase B, the phases of which are shifted from each other by 1/4 wavelength, and the rectangular wave pulse is directly input to the focus information acquisition unit,
The relationship between the actual position of the focus group on the optical axis and the focus information read by the focus information acquisition unit is calibrated,
15. The video camera according to claim 14, wherein the focus information acquisition unit converts a phase shift direction of a B phase with respect to an A phase of the rectangular wave pulse and a count number of the rectangular wave pulse into the focus information. . The position of the focus group acquired by the ring buffer at the time when the focus evaluation value is calculated using the entire autofocus frame that defines the focus evaluation value acquisition area, which is set in the screen for displaying the captured image. When,
From the relationship with the position of the focus group read into the ring buffer at the time when the focus evaluation value immediately before the time when the focus evaluation value has been calculated is completed,
Set the focus evaluation value generation time that can be regarded as the time when the focus evaluation value was actually generated,
The time at which the focus evaluation value stored in the ring buffer has been calculated is the immediately subsequent focus evaluation value reception time, and the time at which the immediately preceding focus evaluation value reception time has been calculated is calculated. Let it be the last focus evaluation value reception time,
Using the relationship between the position of the focus group at the reception time immediately after the focus evaluation value and the position of the focus group at the reception time immediately before the focus evaluation value,
The video camera according to claim 11, wherein a position of the focus group at the focus evaluation value generation time is calculated. Between the previous focus evaluation value reception time and the immediately subsequent focus evaluation value reception time,
The focus evaluation value generation time is set by the time when the scanning line at the center position in the vertical direction of the autofocus frame is scanned from the left end to the right end,
The time interval between the focus evaluation value generation time and the immediately subsequent focus evaluation value reception time is T _0, and the time interval between the immediately previous focus evaluation value reception time and the focus evaluation value generation time is T ₁ , The position of the focus group at the focus evaluation value reception time is FP _a , the position of the focus group at the previous focus evaluation value reception time is FP _b ,
The position FP of the focus group at the focus evaluation value generation time is expressed by the following equation (1)
FP = FP _a − [(FP _a −FP _b ) × {T ₀ / (T ₀ + T ₁ )}] (1)
The video camera according to claim 16, which is given by: Extracting the maximum value of the focus evaluation value stored in the ring buffer until immediately before receiving a command for starting an autofocus operation from the focus controller,
The time at which the maximum value of the extracted focus evaluation value is read as the immediately after focus evaluation value reception time,
Calculate the difference between the current position of the focus group and the position FP of the focus group at the focus evaluation value generation time,
18. The video camera according to claim 17, wherein the focus group is moved to a position FP of the focus group at the calculated focus evaluation value generation time.

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